As the technological development of semiconductors advances, demands for miniaturized packaging and larger data storage capacity have also intensified along the way. In addition to that, because the data processing capacity is constantly increasing, if data units of the same size can be processed at the fastest speed possible in a given unit of time, then data can be processed more efficiently. The most straightforward method for raising the processing speed of semiconductors is to increase its operating frequency, but when the data transfer rate exceeds one gigabyte per second, problems like heat dissipation caused by high wattage, signal time delay, and electromagnetic interference (EMI) also arise, which will impede the production of semiconductors with high performance. This problem has been made even more severe because the traditional medium for data signal transmission is copper circuit, which cannot achieve higher conductivity due to its intrinsically limited conducting property, thus its signal transmission rate cannot be elevated by the method of increasing its conductivity.
Moreover, the signal transmission structure made of metal circuits is more susceptible to the interference of external noises or internal circuits during signal transmission, which in turn leads to erroneous signals being transferred. Therefore, the signal transmission structure has to be equipped with adequate protective measures to prevent the interference mentioned above from affecting signals, and this phenomenon is especially obvious in high-frequency signal transmission. The protective measures will result in increased difficulty to the designs of circuit and additional structures, which will in turn raise the costs of design and production, and cannot improve the current situation.
The traditional method of signal transmission is analog signal transmission, which works by charging conductor with electrical currents, but the current method for processing signals inside circuits is the digital processing method, which can easily distort signals when one type of signal is converted to the other during signal transmission.
In order to resolve the disadvantages resulted from the traditional method of analog signal transmission, the new technology uses optical signal to replace electrical signal for signal transmission, and the most obvious advantage by such change is better quality in signal transmission, since the optical signal is almost unsusceptible to interference of electromagnetic waves and is thus not distorted as much. As a result, there is no need to design a structure for preventing the interference of electromagnetic waves, and this helps reduce the costs of design and production. Therefore, using optical signal for signal transmission has become the main aim for future development.
In the prior arts, the optical transmission structure is designed to be disposed inside the printed circuit board; the process begins by adding a layer of optical conductive layer with organic waveguide film into the printed circuit board, then followed by the integration and packaging of optoelectronic and driving components onto the circuit board; the optical conductive layer can serve as the pathway for optical signal transmission, thereby achieving the aim of high-speed transfer. FIG. 1 shows the invention of U.S. Pat. No. 6,839,476, wherein a core layer 12 is formed on the bottom layer 11, and a plurality of grooves 12a are also formed on core layer 12; an optical fiber 13 is disposed into groove 12a, followed by the formation of a top layer 14 on top of core layer 12, so that optical fiber 13 is embedded within core layer 12; optical fiber 13 is made by enclosing a layer of cladding 13b around a core 13a. The two ends of optical fiber 13 can be fitted with optical transmitting and receiving modules, along with passive optical components, so that the disadvantages of electrical signal transmission can be avoided by sending optical signal via optical fiber 13.
However, because optical fiber 13 needs to be embedded in groove 12a of core layer 12, the core layer 12 has to undergo the grooving process in prior to the above step, followed by the disposition of optical fiber 13 into groove 12a to complete the overall production process. But the disposition of optical fiber 13 into groove 12a is carried out mechanically is similar to the mechanically process of electronic components inserted into the circuit board. As a result, the speed of production is slower and cannot reach the goal of fast production.
Moreover, optical fiber 13 needs to be cut in accordance with the length of groove 12a that it faces beforehand, so that it can then be disposed into groove 12a; this adds an additional step in the overall production process, and hence raises the difficulty of the production process. On the other hand, the uneven length of optical fiber 13 also makes the classification step in the production process more complicated, thereby increasing overall production steps and raising its complication, which in turn results in increased production costs.
Because grooves 12a has to be formed on core layer 12 in order to accept optical fiber 13, it is necessary to leave adequate interval spaces between each of the groove 12a while designing their size, so that optical fiber 13 can be disposed into core layer 12. But under the double influences of the size of interval space and the diameter of optical fiber 13, the optical fiber 13 layout density cannot be elevated.
Furthermore, the optical fiber 13 used to transfer optical signal is made by enclosing a layer of cladding 13b around a core 13a, wherein the inner layer of cladding 13b can serve as a reflecting surface that allows the optical signals to be reflected forwardly and thereby achieving the goal of transmitting signals. On the other hand, optical fiber 13 and circuit board are two different structures and need to be produced independently; afterwards, the two separately produced products also needs to be integrated. Both steps described above increase the difficulty of the overall production process; impede the attainment of mass production, and thus the production cost cannot be lowered further.
Because optical fiber 13 needs to be embedded with core layer 12, the difficulty and cost of the production are increased as a result; on the other hand, the demand of high optical fiber 13 layout density cannot be satisfied either, and all of the above issues require immediate attention and solution from the industry.
Therefore, it is urgent for the industry to provide a circuit board structure of integrated optoelectronic component that can meet the demand of miniaturization for electronic devices, reduce signal loss during signal transmission, shorten conductive pathway, decrease noises, and enhance the quality of optoelectronic signal transmission.